Instrumentation amplifiers may be used to amplify signals generated by sensors such as strain gauges, thermocouples, or low-side or high-side current-sense resistors. Since these signals are in most cases direct current (“DC”) or low-frequency voltages and have amplitudes in the order of millivolts or even microvolts, the detection limit of the instrumentation amplifier is determined by errors such as its offset voltage and flicker noise. To correct for these two errors one common method is to use chopping whereby the offset voltage and flicker noise are up-modulated by a clock signal to frequencies higher than the input signal bandwidth where they cannot have a negative impact upon the DC performance.
An indirect-feedback architecture may be chosen for instrumentation amplifiers, in which the feedback signal is applied to a different port from the input signal. These may be referred to as a current-feedback instrumentation amplifier (“CFIA”). Each of an input port and a feedback port may require a voltage-to-current converter (or transconductor) whose purpose is to convert the input and feedback voltages into currents that are then subtracted in order to close the feedback loop. To correct for the offset voltage of a CFIA, chopping must be applied to both the input and feedback transconductors.
The input and feedback transconductors may be designed such that the clocks implementing chopping have amplitudes that depend on (or track) the input and feedback common-mode (“CM”) voltages respectively. These voltages are not necessarily equal. The dependence on CM voltages can lead to the input and feedback clocks becoming de-synchronized, or out-of-phase, if the input and feedback CM voltages differ significantly, even for short durations of time, as contemplated by embodiments of the present disclosure.